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  • Are flag variables an absolute evil?

    - by dukeofgaming
    I remember doing a couple of projects where I totally neglected using flags and ended up with better architecture/code; however, it is a common practice in other projects I work at, and when code grows and flags are added, IMHO code-spaghetti also grows. Would you say there are any cases where using flags is a good practice or even necessary?, or would you agree that using flags in code are... red flags and should be avoided/refactored; me, I just get by with doing functions/methods that check for states in real time instead. Edit: Not talking about compiler flags

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  • Using "prevent execution of method" flags

    - by tpaksu
    First of all I want to point out my concern with some pseudocode (I think you'll understand better) Assume you have a global debug flag, or class variable named "debug", class a : var debug = FALSE and you use it to enable debug methods. There are two types of usage it as I know: first in a method : method a : if debug then call method b; method b : second in the method itself: method a : call method b; method b : if not debug exit And I want to know, is there any File IO or stack pointer wise difference between these two approaches. Which usage is better, safer and why?

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  • Passing variables from PHP to C++

    - by Alex
    I’m new to this so I’m sorry if my question is trivial. I have the following situation: I need to call a program from PHP and pass some vars and/or sets of key-value pairs to it. Now, my question is: how do I pass these vars, through arguments to the called function (e.g. exec("/path/to/program flag1 flag2 [key1=A,key2=B]");)? Or is there a better method to achieve this? Somebody suggested me to write them into a txt file and pass the path to it to as an argument instead (e.g. exec("/path/to/program path_to_txt_file);), but I’m not to excited about this method.

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  • CONFIG_ATH_USER_REGD variable In Ununtu

    - by BigGenius
    There is a CONFIG_ATH_USER_REGD variable in OpenWrt that allows the user to override the default settings of the wireless NIC. Unfortunately grepping the Arch kernel config doesn't seem to have that, and since OpenWrt has its fair share of hacking and patches, I don't know if that's something they added or that's provided e.g. in compat-wireless. Does this setting exists for Ubuntu or BackTrack-Linux?

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  • Variable number of GUI Buttons

    - by Wakaka
    I have a generic HTML5 Canvas GUI Button class and a Scene class. The Scene class has a method called createButton(), which will create a new Button with onclick parameter and store it in a list of buttons. I call createButton() for all UI buttons when initializing the Scene. Because buttons can appear and disappear very often during rendering, Scene would first deactivate all buttons (temporarily remove their onclick, onmouseover etc property) before each render frame. During rendering, the renderer would then activate the required buttons for that frame. The problem is that part of the UI requires a variable number of buttons, and their onclick, onmouseover etc properties change frequently. An example is a buffs system. The UI will list all buffs as square sprites for the current unit selected, and mousing over each square will bring up a tooltip with some information on the buff. But the number of buffs is variable thus I won't know how many buttons to create at the start. What's the best way to solve this problem? P.S. My game is in Javascript, and I know I can use HTML buttons, but would like to make my game purely Canvas-based. Create buttons on-the-fly during rendering. Thus I will only have buttons when I require them. After the render frame these buttons would be useless and removed. Create a fixed set of buttons that I'm going to assume the number of buffs per unit won't exceed. During each render frame activate the buttons accordingly and set their onmouseover property. Assign a button to each Buff instance. This sounds wrong as the buff button is a part of the GUI which can only have one unit selected. Assigning a button to every single Buff in the game seems to be overkill. Also, I would need to change the button's position every render frame since its order in the unit's list of buffs matter. Any other solutions? I'm actually quite for idea (1) but am worried about the memory/time issues of creating a new Button() object every render frame. But this is in Javascript where object creation is oh-so-common ({} mainly) due to automatic garbage collection. What is your take on this? Thanks!

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  • How do I access variable values from one view controller in another?

    - by Thomas
    Hello all, I have an integer variable (time) in one view controller whose value I need in another view controller. Here's the code: MediaMeterViewController // TRP - On Touch Down event, start the timer -(IBAction) startTimer { time = 0; // TRP - Start a timer timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(updateTimer) userInfo:nil repeats:YES]; [timer retain]; // TRP - Retain timer so it is not accidentally deallocated } // TRP - Method to update the timer display -(void)updateTimer { time++; // NSLog(@"Seconds: %i ", time); if (NUM_SECONDS == time) [timer invalidate]; } // TRP - On Touch Up Inside event, stop the timer, decide stress level, display results -(IBAction) btn_MediaMeterResults { [timer invalidate]; NSLog(@"Seconds: %i ", time); ResultsViewController *resultsView = [[ResultsViewController alloc] initWithNibName:@"ResultsViewController" bundle:nil]; [self.view addSubview:resultsView.view]; } And in ResultsViewController, I want to process time based on its value ResultsViewController - (void)viewDidLoad { if(time < 3) {// Do something} else if ((time > 3) && (time < 6)) {// Do something else} //etc... [super viewDidLoad]; } I'm kind of unclear on when @property and @synthesize is necessary. Is that the case in this situation? Any help would be greatly appreciated. Thanks! Thomas

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  • Why I do not see a static variable in a loop?

    - by Roman
    I have a static method which sets a variable: static String[] playersNames; public static void setParameters(String[] players) { playersNames = players; } Then I have a static block: static { JRadioButton option; ButtonGroup group = new ButtonGroup(); // Wright a short explanation of what the user should do. partnerSelectionPanel.add(new JLabel("Pleas select a partner:")); // Generate radio-buttons corresponding to the options available to the player. // Bellow is the problematic line causing the null pointer exception: for (String playerName: playersNames) { final String pn = playerName; option = new JRadioButton(playerName, false); option.addActionListener(new ActionListener(){ @Override public void actionPerformed(ActionEvent evt) { partner = pn; } }); partnerSelectionPanel.add(option); group.add(option); } partnerSelectionPanel.add(label); // Add the "Submit" button to the end of the "form". JButton submitButton = new JButton("Submit"); submitButton.addActionListener(new ActionListener(){ @Override public void actionPerformed(ActionEvent evt) { partnerSelected(); } }); partnerSelectionPanel.add(submitButton); } Compiler does not complain about anything but when I try to execute the code I get problems. In this place SelectPartnerGUI.setParameters(players); I have: Exception in thread "main" java.lang.ExceptionInitializerError. and it is cause by java.lang.NullpointerException at this place for (String playerName: playersNames). Does my program do not see the palyersNames?

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  • How to access global variable in a view in Ruby on Rails?

    - by ben
    I have a User model. I have a Session controller, in which I have a global user variable that is assigned as follows: $user = User.authenticate(params[:session][:email], params[:session][:password]) (I've made user global just to try to solve this problem, so if there's a better way please let me know!) I need to use the email of the logged in user as a parameter to send to Flex part of my website. At the moment I'm creating the link as follows: <%= link_to "secondpage", secondpage_path(:email => @session.$user.email) But I'm getting the following error: compile error /Users/benhartney/rails_projects/talk/app/views/layouts/_header.html.erb:12: syntax error, unexpected tGVAR ..._path(:email = @session.$user.email) ).to_s); @output_buffe... There's also a little arrow pointing at $user If I remove the $ from $user, I get this error: undefined method `user' for nil:NilClass If I remove the (:email => @session.user.email) part, everything works fine, so I think all of the code except for this is ok. Can anyone tell me what I'm doing wrong? Thanks for reading!

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  • Variable length argument list - How to understand we retrieved the last argument?

    - by hkBattousai
    I have a Polynomial class which holds coefficients of a given polynomial. One of its overloaded constructors is supposed to receive these coefficients via variable argument list. template <class T> Polynomial<T>::Polynomial(T FirstCoefficient, ...) { va_list ArgumentPointer; va_start(ArgumentPointer, FirstCoefficient); T NextCoefficient = FirstCoefficient; std::vector<T> Coefficients; while (true) { Coefficients.push_back(NextCoefficient); NextCoefficient = va_arg(ArgumentPointer, T); if (/* did we retrieve all the arguments */) // How do I implement this? { break; } } m_Coefficients = Coefficients; } I know that we usually pass an extra parameter which tells the recipient method the total number of parameters, or we pass a sentimental ending parameter. But in order to keep thing short and clean, I don't prefer passing an extra parameter. Is there any way of doing this without modifying the method signature in the example?

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  • Improved technique to store a filename in a variable?

    - by SDGuero
    Greetings, I need to store the filename of a log into a variable so my script can perform some checks on the daily log files. These logs always have a different name because they have a timestamp in the name. Currently I'm using a hodge podged method that pipes an ls command to sed, sort, cut, and tail in order to get the name out. CRON_LOG=$(ls -1 $LOGS_DIR/fetch_cron_{true,false}_$CRON_DATE*.log 2> /dev/null | sed 's/^[^0-9][^0-9]*\([0-9][0-9]*\).*/\1 &/' | sort -n | cut -d ' ' -f2- | tail -1 ) UPDATE: $CRON_DATE is supplied as an argument to the script. It is the date (to the day) that the log was created on. Sometimes multiple logs will exist for the same day so I want this to get the most recent one. A typical filename is fetch_cron_false_031810090452.log I'm pretty sure I kluged this together from some stuff I found google a few months ago. it works now but I'm not really happy with the technique. I have some ideas about how to do this better but I have had great success on this site before and thought it might be best to refer to the stackoverflow gods first. All answers are greatly appreciated. Thanks, Ryan

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  • python - tkinter - update label from variable

    - by Tom
    I wrote a python script that does some stuff to generate and then keep changing some text stored as a string variable. This works, and I can print the string each time it gets changed. Problems have arisen while trying to display that output in a GUI (just as a basic label) using tkinter. I can get the label to display the string for the first time... but it never updates. This is really the first time I have tried to use tkinter, so it's likely I'm making a foolish error. What I've got looks logical to me, but I'm evidently going wrong somewhere! from tkinter import * outputText = 'Ready' counter = int(0) root = Tk() root.maxsize(400, 400) var = StringVar() l = Label(root, textvariable=var, anchor=NW, justify=LEFT, wraplength=398) l.pack() var.set(outputText) while True: counter = counter + 1 #do some stuff that generates string as variable 'result' outputText = result #do some more stuff that generates new string as variable 'result' outputText = result #do some more stuff that generates new string as variable 'result' outputText = result if counter == 5: break root.mainloop() I also tried: from tkinter import * outputText = 'Ready' counter = int(0) root = Tk() root.maxsize(400, 400) var = StringVar() l = Label(root, textvariable=var, anchor=NW, justify=LEFT, wraplength=398) l.pack() var.set(outputText) while True: counter = counter + 1 #do some stuff that generates string as variable 'result' outputText = result var.set(outputText) #do some more stuff that generates new string as variable 'result' outputText = result var.set(outputText) #do some more stuff that generates new string as variable 'result' outputText = result var.set(outputText) if counter == 5: break root.mainloop() In both cases, the label will show 'Ready' but won't update to change that to the strings as they're generated later. After a fair bit of googling and looking through answers on this site, I thought the solution might be to use update_idletasks - I tried putting that in after each time the variable was changed, but it didn't help. It also seems possible I am meant to be using trace and callback somehow to make all this work...but I can't get my head around how that works (I tried, but didn't manage to make anything that even looked like it would do something, let alone actually worked). I'm still very new to both python and especially tkinter, so, any help much appreciated but please spell it out for me if you can :)

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  • Objective C, Linking Error with extern variable..

    - by LCYSoft
    I have a very simple java code like this. I don't have any idea how to do this in Objective C. Especially, the static part which calls the getLocalAddress() method and assign it into the static string variable. I know how to set a static variable and a static method in Objective but I dont know how to implement that static { } part in java. Thanks in advance... public class Address { public static String localIpAddress; static { localIpAddress = getLocalIpAddress(); } public Address() { } static String getLocalIpAddress() { //do something to get local ip address } } I added this in my .h file #import <Foundation/Foundation.h> extern NSString *localIpAddress; @class WifiAddrss; @interface Address : NSObject { } @end And my .m file looks like #import "Address.h" #import "WifiAddress.h" @implementation Address +(void)initialize{ if(self == [Address class]){ localIpAddress = [self getLocalIpAddress]; } } +(NSString *)getLocalIpAddress{ return address here } -(id)init{ self = [super init]; if (self == nil){ NSLog(@"init error"); } return self; } @end And Now I am getting a linking error and it complains about "extern NSString *localIpAddress" part. If I change the extern to static, it works fine. But what I wanted to do is that I want make the scope of "localIpAddress" variable as grobal. Since if I put "static" in front of a variable in Objective-C then the variable is only visible in the class. But this time, I want to make that as a grobal variable. So my question is how to make "localIpAddress" variable as a grobal variable which is initialized once when the first time Address class is created.. Thanks in advance...

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  • Track user through Google Universal Analytics

    - by raygo
    I want to track a user from my site, give an id to Google Analytics and later be able to see which pages that id visited and for how long did that id view the pages. I've tried custom variables with the classic analytics. I tried enabling the User-ID feature in the Universal Analytics. Neither of these have given me what I want yet. Is there any way to accomplish this with Universal Analytics? UPDATE This is a sample code with a user whose id is 2. I try to set the userid in different ways to see if at least in one way it shows. <script> (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){ (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o), m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m) })(window,document,'script','//www.google-analytics.com/analytics.js','ga'); ga('create', 'UA-XXXXXXX-1', 'domain.com', { 'userId': '2' }); ga('set', '&uid', '2'); // Set the user ID using signed-in user_id. var dimensionValue = '2'; ga('set', 'dimension1', dimensionValue); ga('send', 'pageview'); </script>

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  • Using a variable in jQuery to perform a function...

    - by DevlshOne
    Can someone tell me what's wrong with this code? It doesn't seem to be recognizing the '#del[' + cid + ']' selector, at all. Which is the exact name of the ID in my PHP code. $(function() { var cid = '<?=$row['c_id'];?>'; $('#del[' + cid + ']').click(function() { alert('clicked!'); var oldqty = <?=$row['qty'];?>; var qtyID = "'" + '#qty' + cid + "'"; alert(qtyID); if ($(qtyID).is(':checked')) { $(this).(function() { $(this).val(0); }); }; if($(qtyID).not(':checked')) { $(this).(function() { $(this).val(0); }); }; }); }); Here's the PHP code that implement $row['c_id']: echo "<input class=\"number aln_center\" type=\"text\" name=\"qty[" . $row['c_id'] . "]\" id=\"qty" . $row['c_id'] . "\" value=\"" . $row['qty'] . "\" size=\"3\" onchange=\"return validateChgMLQty('qty" . $row['c_id'] . "'," . $row['qty'] . ");\" />\n"; echo "<input type=\"hidden\" name=\"telco[" , $row['c_id'] . "]\" id=\"telco" . $row['c_id'] . "\" value=\"" . $row['btelco'] . "\" />\n"; echo "<br />Delete\n"; echo "<input type=\"checkbox\" name=\"del[" . $row['c_id'] . "]\" id=\"del" . $row['c_id'] . "\" />\n"; I'm trying to get the value in the input statement to change to "0" if the "Delete" checkbox is clicked and then return back to it's original contents when unchecked. It never even gets to the first alert box, so it has nothing to do with qtyID and when viewing source, the 'var cid' line is populated with the correct integer passed from PHP variable $row['c_id'].

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  • MySQL Triggers - How to capture external web variables? (eg. web username, ip)

    - by Ken
    Hi, I'm looking to create an audit trail for my PHP web app's database (eg. capture inserts, updates, deletes). MySQL triggers seem to be just the thing -- but how do I capture the IP address and the web username (as opposed to the mysql username, localhost) of the user who invoked the trigger? Thanks so much. -Ken P.S. I'm working with this example code I found: DROP TRIGGER IF EXISTS history_trigger $$ CREATE TRIGGER history_trigger BEFORE UPDATE ON clients FOR EACH ROW BEGIN IF OLD.first_name != NEW.first_name THEN INSERT INTO history_clients ( client_id , col , value , user_id , edit_time ) VALUES ( NEW.client_id, 'first_name', NEW.first_name, NEW.editor_id, NEW.last_mod ); END IF; IF OLD.last_name != NEW.last_name THEN INSERT INTO history_clients ( client_id , col , value , user_id , edit_time ) VALUES ( NEW.client_id, 'last_name', NEW.last_name, NEW.editor_id, NEW.last_mod ); END IF; END; $$

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  • Strange behavior with Powershell scriptblock variable scope and modules, any suggestions?

    - by DanMan
    NOTE: I'm using PowerShell 2.0 on Windows Vista. I'm trying to add support for specifying build arguments to psake, but I've run into some strange PowerShell variable scoping behavior dealing specifically with calling functions that have been exported using Export-ModuleMember (which is how psake exposes it's main method). Following is a simple PowerShell module to illustrate (named repoCase.psm1): function Test { param( [Parameter(Position=0,Mandatory=0)] [scriptblock]$properties = {} ) $defaults = {$message = "Hello, world!"} Write-Host "Before running defaults, message is: $message" . $defaults #At this point, $message is correctly set to "Hellow, world!" Write-Host "Aftering running defaults, message is: $message" . $properties #At this point, I would expect $message to be set to whatever is passed in, #which in this case is "Hello from poperties!", but it isn't. Write-Host "Aftering running properties, message is: $message" } Export-ModuleMember -Function "Test" To test the module, run the following sequence of commands (be sure you're in the same directory as the repoCase.psm1): Import-Module .\repoCase.psm1 #Note that $message should be null Write-Host "Before execution - In global scope, message is: $message" Test -properties { "Executing properties, message is $message"; $message = "Hello from properties!"; } #Now $message is set to the value from the script block. The script block affected only the global scope. Write-Host "After execution - In global scope, message is: $message" Remove-Module repoCase The behavior I expected was for the script block I passed to Test to affect the local scope of Test. It is being 'dotsourced' in, so any changes it makes should be within the scope of the caller. However, that's not what's happening, it seems to be affecting the scope of where it was declared. Here's the output: Before execution - In global scope, message is: Before running defaults, message is: Aftering running defaults, message is: Hello, world! Executing properties, message is Aftering running properties, message is: Hello, world! After execution - In global scope, message is: Hello from properties! Interestingly, if I don't export Test as a module and instead just declare the function and invoke it, everything works just like I would expect it to. The script block affects only Test's scope, and does not modify the global scope. I'm not a PowerShell guru, but can someone explain this behavior to me?

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  • How to handle optional variables of an object in Java?

    - by Arvanem
    Hi folks, For my trading program, I have a Merchant class. A given Merchant object may or may not have a particular special quality or bundle of special qualities. For example, one Merchant object may have the Stockbroker quality, another Merchant may have the Financial Services and Stockbroker qualities, and another Merchant may have no special qualities at all. My initial thought was to create a HashMap and a Qualities class as follows: Map<Qualities, Boolean> merchantQualities = new HashMap<Qualities, Boolean>(); The only problem is, there are at least 50 possible special qualities for Merchants, such that it would be extremely tiresome to subclass all the qualities from the Quality class. Is there a better way of coding for these optional special qualities and representing them in the Merchants class than a HashMap and subclassing a Qualities class?

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  • c# - How do you get a variable's name as it was physically typed in its declaration?

    - by Petras
    The class below contains the field city. I need to dynamically determine the field's name as it is typed in the class declaration i.e. I need to get the string "city" from an instance of the object city. I have tried to do this by examining its Type in DoSomething() but can't find it when examining the contents of the Type in the debugger. Is it possible? public class Person { public string city = "New York"; public Person() { } public void DoSomething() { Type t = city.GetType(); string field_name = t.SomeUnkownFunction(); //would return the string "city" if it existed! } } Some people in their answers below have asked me why I want to do this. Here's why. In my real world situation, there is a custom attribute above city. [MyCustomAttribute("param1", "param2", etc)] public string city = "New York"; I need this attribute in other code. To get the attribute, I use reflection. And in the reflection code I need to type the string "city" MyCustomAttribute attr; Type t = typeof(Person); foreach (FieldInfo field in t.GetFields()) { if (field.Name == "city") { //do stuff when we find the field that has the attribute we need } } Now this isn't type safe. If I changed the variable "city" to "workCity" in my field declaration in Person this line would fail unless I knew to update the string if (field.Name == "workCity") //I have to make this change in another file for this to still work, yuk! { } So I am trying to find some way to pass the string to this code without physically typing it. Yes, I could declare it as a string constant in Person (or something like that) but that would still be typing it twice. Phew! That was tough to explain!! Thanks Thanks to all who answered this * a lot*. It sent me on a new path to better understand lambda expressions. And it created a new question.

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  • Public static variables and Android activity life cycle management

    - by jsstp24n5
    According to the documentation the Android OS can kill the activity at the rear of the backstack. So, say for example I have an app and open the Main Activity (let's call it Activity A). In this public activity class I declare and initialize a public static variable (let's call it "foo"). In Activity A's onCreate() method I then change the value of "foo." From Activity A the user starts another activity within my app called Activity B. Variable "foo" is used in Activity B. Activity B is then paused after the user navigates to some other activities in other apps. Eventually, after a memory shortage occurs, Activity A then Activity B can be killed. After the user navigates back to my app it restarts (actually "recreates") activity B. What happens: 1) Will variable "foo" at this point have the value that was set to it when Activity A's onCreate() method ran? 2) Variable "foo" does not exist? 3) Variable "foo" exists and but is now the initialized value and not the value set in Activity A's onCreate() method?

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  • How to find the right object in a Rails controller based on two variables?

    - by sscirrus
    Hi everyone, I have a three-table system: Companies, Customers, and Matches. The matches include, for example, private notes that each party makes about the other and some options they can set regarding the other. I have two sets of views centered around Companies and Customers for each party to look at the other and modify their notes and settings. # Customers Controller def show @customer = Customer.find(params[:customer]) @matchings = @candidate.matchings.find... @company = Company.find(params[:company]) end Obviously the @matchings is incomplete. Given that @matchings has fields customer_id and company_id, how do I find the right matching record? Thank you!

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  • Objective C instance variables - Newbie

    - by Dwayne King
    OK - so I'm sure my confusion here is just a result of being stuck in a "Java mindset" and not understanding how Obj C differs in this case. In Java, I can declare a variable in a class, like this, and each instance of that class will have it's own: MyClass { String myVar; MyClass() { // constructor } } In Obj C I tried to do the same thing by declaring a variable only in the .m file like this: #import "MyClass.h" @implementation MyClass NSString *testVar; @end My expectation here was that this variable has a scope limited to this class. So I created a second class (identical): #import "MySecondClass.h" @implementation MySecondClass NSString *testVar; @end What I'm seeing (and has me baffled) is that changing the variable in one class, affects the value seen in the other class. In fact, if I set a breakpoint, and then "Jump to Definition" of the variable, it takes me to th I've created an extremely small XCode project that demonstrates the problem here Nothing more humbling than moving to a new language :) Thanks in advance.

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  • sys.path() and PYTHONPATH issues

    - by Justin
    I've been learning Python, I'm working in 2.7.3, and I'm trying to understand import statements. The documentation says that when you attempt to import a module, the interpreter will first search for one of the built-in modules. What is meant by a built-in module? Then, the documentation says that the interpreter searches in the directories listed by sys.path, and that sys.path is initialized from these sources: the directory containing the input script (or the current directory). PYTHONPATH (a list of directory names, with the same syntax as the shell variable PATH). the installation-dependent default. Here is a sample output of a sys.path command from my computer using python in command-line mode: (I deleted a few so that it wouldn't be huge) ['', '/usr/lib/python2.7', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PIL', '/usr/lib/python2.7/dist-packages/gst-0.10', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/pymodules/python2.7', '/usr/lib/python2.7/dist-packages/ubuntuone-couch', '/usr/lib/python2.7/dist-packages/ubuntuone-storage-protocol'] Now, I'm assuming that the '' path refers to the directory containing the 'script', and so I figured the rest of them would be coming from my PYTHONPATH environmental variable. However, when I go to the terminal and type env, PYTHONPATH doesn't exist as an environmental variable. I also tried import os then os.environ, but I get the same output. Do I really not have a PYTHONPATH environmental variable? I don't believe I ever specifically defined a PYTHONPATH environmental variable, but I assumed that when I installed new packages they automatically altered that environment variable. If I don't have a PYTHONPATH, how is my sys.path getting populated? If I download new packages, how does Python know where to look for them if I don't have this PYTHONPATH variable? How do environment variables work? From what I understand, environment variables are specific to the process for which they are set, however, if I open multiple terminal windows and run env, they all display a number of identical variables, for example, PATH. I know there file locations for persistent environment variables, for example /etc/environment, which contains my PATH variable. Is it possible to tell where a persistent environment variable is stored? What is the recommended location for storing new persistent environment variables? How do environment variables actually work with say, the Python interpreter? The Python interpreter looks for PYTHONPATH, but how does it work at the nitty-gritty level?

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  • Is it good practice to export variables in Perl?

    - by gvkv
    I'm finding it very convenient to pass configuration and other data that is read or calculated once but then used many times throughout a program by using Perl's use mechanism. I'm doing this by exporting a hash into the caller's namespace. For example: package Myconfiguration; my %config; sub import { my $callpkg = caller(0); my $expsym = $_[1]; configure() unless %config; *{"$callpkg\::$expsym"} = \%config; } and then in other modules: use MyConfiguration (loc_config_sym); if ( $loc_config_sym{paramater} ) { # ... do stuff ... } However, I'm not sure about this as a best practice. Is it better to add a method that returns a hash ref with the data? Something else?

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